So you turn the headlights on, one comes up, and then, a few seconds later the other one lights.
Next time you try, you find main beam has gone down on the other one, but only for a while.
The solution on a 97 'trak with 140000 on the clock .... the poxy jap connectors to the back of the headlamp bulbs have melted. Replaced by a pair of Joe Lucas connectors from the wiring loom of, I think, a Morris 1100 .... result sanity.
BTW, if you start using high wattage, say 130/90 watt headlamp bulbs, you will really cook the connectors and wiring which IMHO is marginal for 60/55 W.
Also, can you still get those hi watt bulbs, or has our poxy nanny state got anally retentive about that too